数字信号发生器参数对土壤电导率仪测量结果的影响

Influence of Parameters of Digital Signal Generator on Measurement Results of Soil Conductivity Meter

针对基于电流-电压四端法的车载式土壤电导率测量系统激励源会随着土壤负载的变化而波动,从而影响测量结果的问题,采用波形标准、抗干扰能力强的可调频、调幅数字信号发生器代替普通激励源,通过探究信号发生器不同频率、幅值对实验结果的影响,进而找到最适合车载式测量系统的频率与幅值。为减少大田复杂环境对实验结果的影响,实验分为实验室探究性实验和大田验证性实验。实验室探究性实验设置5个幅值和20个频率进行实验,通过分析60组样本的6000组实验室数据可知,同频率下幅值越大实验效果越好,最佳幅值为10 V;同幅值下随着频率的增加土壤电导率呈现先增加后减小的抛物线趋势,幅值10 V、频率100 Hz梯度下土壤电导率测量值和参考值决定系数R^(2)达到0.9505,实验效果最佳。大田验证性实验最佳幅值仍为10 V,但由于土壤负载随着电极间距的变大而变大,大田验证性实验最佳频率变为1 kHz,幅值10 V、频率1 kHz梯度下电导率测量值和参考值R;为0.8484,为最佳实验效果。

For the vehicle-mounted soil conductivity measurement system based on the current-voltage four-terminal method,the excitation source will fluctuate with the change of soil load,thereby affecting the measurement results.Using waveform standard and strong anti-interference ability adjustable frequency and amplitude modulation digital signal generator instead of ordinary excitation source,by exploring the influence of different frequencies and amplitudes of the signal generator on the experimental results,and then the most suitable frequency and amplitude were fond for the vehicle-mounted measurement system value.In order to reduce the impact of complex environment of field on the experimental results,the experiment was divided into laboratory exploratory experiments and field confirmatory experiments.Laboratory exploratory experiments set five amplitudes and 20 frequencies for experiments.By analyzing 6000 sets of laboratory data of 60 sets of samples,it can be known that the larger the amplitude at the same frequency was,the better the experimental effect was,and the best amplitude was 10 V.Under the same amplitude,with the increase of frequency,the soil conductivity showed a parabolic trend which was increased first and then decreased.The measured value of the soil conductivity and the reference value determination coefficient R^(2) reached 0.9505 at the amplitude of 10 V and frequency of 100 Hz,and the experimental effect was the best.The best amplitude of the field confirmatory experiment was still 10 V,but because the soil load was increased with the increase of the electrode spacing,the best frequency of the field confirmatory experiment became 1 kHz,with an amplitude of 10 V and a frequency of 1 kHz.The measured value of conductivity and the reference value R;were 0.8484,which was the best experimental effect.